Background Helmet therapy is widely accepted in the treatment of severe positional plagiocephaly. The improvement of the cranial asymmetry under therapy is evident, but parents are also concerned about the ear shift. Our study investigated the influence of helmet therapy on the position of the ears and analyzed the reliability of clinical observations regarding cranial asymmetry and ear shift.

Methods Three-dimensional stereophotogrammetry of 80 infants with severe positional plagiocephaly was performed before and after helmet therapy. The cranial vault asymmetry index (CVAI) and ear shift were measured and statistically compared. The correlation between the change of CVAI and ear shift was investigated. Three surgeons visually evaluated the treatment results on three-dimensional images independently with a standard questionnaire. The results were compared with the three-dimensional measurements.

Results Sixty infants had a relevant initial ear shift. Under therapy, the shift was improved significantly by a mean of 29.8% (P < 0.001). Twenty infants with an initial straight ear line statistically deteriorate under therapy (P < 0.0001). We found no strong linear correlation between the changes of the CVAI and the ear shift. Analysis of the questionnaire revealed a good correlation between the clinical impression and three-dimensional measurements for the head asymmetry, whereas observations regarding changes in the ear shift were not reliable.

Conclusions Helmet treatment significantly improves an initial malposition of the external ear in infants with positional plagiocephaly. A severe ear shift can be associated with a moderate CVAI and vice versa. In contrast to the CVAI, small changes of the ear shift cannot be evaluated reliably by clinical investigation.